The present invention relates to a power driven swivel connection for turning hanging loads about an upright axis, having a rotor joined by axial and radial bearings with a stator, at least one hydraulic duct running from the stator into the rotor by way of a rotary connection and a driving unit for acting on and turning the rotor in relation to the stator. The driving unit is made up of a collar on the stator or rotor with radial or axial cylinders therein having hydraulic cam drivers extending past a radial or (as the case may be) an axial face of the collar for driving against cams of a cam box on the stator (if the collar is joined with the rotor) or otherwise on the rotor. For timed distribution of hydraulic liquid to the cylinders so that the drivers are only pushed against such cam parts that the resultant is in the desired direction of swivel, a ported distribution spool is liquid-tightly seated within the collar for forcing liquid into the cylinders and letting it off in turn. The hydraulic ducts running from the stator to the rotor are, for example, for connection with the actuator of a clam-shell bucket. The pressure-tight rotary connections are needed for stopping tangling of hoses on swivelling the load. As noted, the driving unit may be a radial or an axial piston motor, while the cam box may be the rotor or the stator.
A swivel connection with a radial piston motor has been put forward in the prior art (see German Pat. No. 2,338,736) having two rotary joints running through the interface of a radial plain bearing, the interface being between a neck of the stator and the rotor. The rotor is furthermore supported by way of an axial rolling element bearing on a shoulder of the collar or cylinder drum of the motor. At the lower end of the hydraulic motor there are furthermore, in the space between the collar and the cam box, two washers acting as plain bearings in the case of a hanging load, and as thrust bearings when the bucket is pressed against the earth etc. When put into general use, this bearing system has, however, not given the desired effects, and specially on supporting or digging heavy loads, more specially when the bucket was acted upon by axial and radial blows, parts of the stator near the radial plain bearing were frequently broken and damaged. A further point is that the bearing gap with the rotary connections therein is open at one end on the outer side of the motor where full sealing is not possible so that there are losses of hydraulic liquid, this being responsible for the building up of dirt coatings on the housing and nearby parts and structures. Because the rotor connections or ports are generally high up on the motor housing, the hoses joined up at this position and running to the bucket are more likely to be damaged than if they were placed lower down. A further shortcoming is the generally great overall height and the great weight, caused thereby, of the swivel connection.
In the case of a further swivel connection designed on the same lines and whose cam box is constitutes the stator and whose collar is constitutes the rotor, the timing or distribution spool being locked on the stator (see German Offenlegungsschrift specification No. 2,838,428), the hydraulic ducts for operation of the bucket are by way of axial holes through the distribution spool from the stator to the rotor. The rotary connections are, in this case, at the lower part of a cylindrical interface between the distribution spool and the rotor. Because of the stiff connection between the distribution spool and the stator, there are, it is true, no sealing troubles at the connections of the hydraulic ducts between the distribution spool and the stator, but, however, for cutting down the forces acting on the distribution spool as a reaction to the effect of outside forces on the motor, it is necessary for complex bearings to be used to be generally free of play. Because, more specially, when working with heavy loads and blows, material is likely to be deformed, such deformation not being stopped by the bearings, the distribution spool and the parts, touching it, have a higher wear rate, this more specially being true on use with heavy loads.